Flexographic printing is a method of direct rotary printing that uses a resilient relief image carrier to print articles such as cartons, bags, labels, newspapers, food or candy wrappers or books. Flexographic printing has found particular application in packaging, where it has displaced rotogravure and offset lithography printing techniques in many cases. Flexographic plates can be prepared from a printing plate precursor having a layer consisting of a photo-polymerizable composition, which generally comprises an elastomeric binder, at least one monomer and a photo-initiator. Early patents on flexographic printing plates include U.S. Pat. Nos. 3,960,572, 3,951,657, 4,323,637 and 4,427,759, the disclosure of each of which is entirely incorporated herein by reference.
Fabrication of electronic circuit elements using metal nanoparticle liquid deposition techniques is of profound interest as such techniques provide potentially low-cost alternatives to conventional mainstream amorphous silicon technologies for electronic applications such as thin film transistors (TFTs), light-emitting diodes (LEDs), RFID tags, photovoltaics, etc. However the deposition and/or patterning of functional electrodes, pixel pads, and conductive traces, lines and tracks which meet the conductivity, processing, and cost requirements for practical applications have been a great challenge.
Flexographic inks may be water- or solvent-based. Flexographic inks are known as liquid inks because of their low viscosity: 10 to 100 cP under printing conditions. Prints produced by flexography can fulfill a wide range of functional effects other than the provision of information such as antistatic properties, for example, for packaging for electronic components sensitive to electrical discharges, and electroconductive properties.
Previous approaches to conductive inkjet ink formulations have used silver nanoparticles stabilized with alkylamines in a blend of terpineol and dodecane to formulate a low-viscosity (less than 5 cP) with a silver loading of 40% by weight, for example, as described in U.S. Pat. No. 7,270,694, which is incorporated by reference herein in its entirety. However, flexographic inks formulations typically require a higher viscosity and metal loading than inkjet ink formulations.